Different types of light emitting diodes (“LEDs”) can have different forward built-in voltages (or junction voltages). For example, gallium nitride/indium gallium nitride (GaN/InGaN) based blue and green LED dies typically operate at a forward built-in voltage of about 3 volts direct current (“DC”). Aluminum indium gallium phosphide (AlInGaP) based LED dies may have a forward built-in voltage around 2 volts DC. To supply power to the LED dies, power supplies typically include AC/DC rectifiers, DC/DC converters, power conditioners, and/or other suitable components. Such power supplies, however, can operate more efficiently when a difference between their output voltage and input voltage is smaller. Thus, LEDs operating at higher voltages (e.g., 24 volts, 48 volts, etc.) than the forward built-in voltage of 3 volts are often desired.
One conventional technique of achieving high input voltage in LEDs is serially coupling a plurality of LED dies in an array. For example, four GaN/InGaN LED dies may be serially coupled to operate at 12 volts, or eight GaN/InGaN LED dies may be serially coupled to operate at 24 volts. However, such a technique limits the number of possible array configurations. For example, with 3-volt GaN/InGaN LED dies, the possible number of LED dies in an array has to be 16 or 32 for an input voltage of 48 volts, and 20 or 40 for an input voltage of 60 volts.
LED dies typically operate most efficiently around an “optimal” flux level per unit area (commonly represented as lumen/die area) due to a peak in efficiency corresponding to a particular current density in the LED dies. By limiting the possible number of LED dies in an array based on the input voltage, the LED dies may not operate at the “optimal” flux level. For example, in a 700 lumen array operating at 24 volts, the array may include 8 or 16 LED dies with each LED die having a flux level of 84 or 42 lumens/die area, respectively. If the “optimal” flux level is 60 lumens/die area, then neither configuration is “optimal.” Accordingly, improved techniques may be desirable for forming arrays of SSL devices to accommodate high input voltages while at least approximating the “optimal” flux level per unit area.